Ball mill



P. A. GOESER Jan. 2, 1962 BALL MILL 2 Sheets-Sheet 1 Filed Aug. 26, 1959 Fig. 7

Jnvenfor: PAUL 1404057 qozszfl P. A. GOESER Jan. 2, 1962 BALL MILL 2 Sheets-Sheet 2 Filed Aug. 26, 1959 Fig. 3

Jnvemor:

PAUL AUG 057 .055? By flWW Aqz' United States Patent Filed Aug. 26, 1959, Ser. No. 836,159 Claims priority, application Germany Sept. 1, 1958 6 Claims. (Cl. 241-472) The invention relates to ball mills or grinders and more particularly to ball mills for milling dyes, creams, min erals and the like. Ball mills of this type are provided with a cylindrical mixing drum. The manner in which these mills operate is such that the drum which is usually horizontally disposed is filled to between 20 and 55% with the grinding bodies such as balls. The rotation of the drum causes the bodies or balls to be raisedup. As soon as the upper surface of the bodies exceeds the angle of flow the grinding bodies roll downwardly. The material disposed between the bodies or balls during this rolling movement is thus subjected to friction or grinding and is partly also crushed.

Generally the interior of such ball grinder is not provided with inserts of any kind. It has been found, however, that in the event that liquids are added which have a lubricating effect the raising of the heap of the milling bodies becomes uncertain. It may happen that the entire batch of grinding bodies slides down on the inner surface of the grinding drum. Under these conditions either no movement at all, or greatly reduced movement takes place between the grinding bodies relative to each other so that the grinding efficiency of the mill is considerably reduced. The inner wall of the drum then constitutes practically the only working surface thus greatly reducing the working efficiency. Moreover, the resultant onesided grinding causes premature destruction of the grind ing bodies or balls and excessive wear of the inner wall of the drum. n

In recognition of this fact it has already'been proposed to make the cross-section of the drum not circular but rather square. Other proposals have been in the direction of providing the drum wall with inherent or welded on raised portions to impart sliding resistance for the grinding bodies to the wall of the drum. It is possible by means of such resistance conformations to prevent the sliding of the grinding bodies extensively. However, the wear of these conformations is considerable, so that replacement is necessary within relatively short time intervals. Such correction Work involves considerable difliculties and results in correspondingly extensive plant interruptions of the ball mill. Operations involving solution vapors of explosive nature in such cases present al.- most insurmountable difficulties. i

It is possible to eliminate the shortcomings described to quite an extent if, as likewise 'known from the prior art, driver rods are provided inside of and longitudinally of the drum and at a distance from the drum 'wall,

which rotate with the drum. Such'driver rods hereto-" fore were provided in the interior of the drum by special built-in components, for example, by providing radialarms between the driver rods and a centrally mounted shaft. However, this type of construction did not prove to be satisfactory, because when operating with wet material or with materials having more or less oily or glueing characteristics, material portions or parts adhered to the built in components atleast temporarily. The adhering material is released in smaller or larger batches in a manner which cannot be controlled, thereby afiecting the ground product rather adversely.

It is, therefore, an object of the invention to provide a ball mill drum which is devoid of built-in obstructions other than driver rods.

In accordance with the invention the driver rods are supported with their ends in supporting positions in the end walls of the drum from the outside and are interchangeable from the outside.

It is a further object of the invention to provide a ball mill drum which has a totally unobstructed interior except for the driver rods and in which the drive shaft is eliminated by journalling the drum in shaft stubs which engage the outside of the end walls of the drum.

Inasmuch as the interior of the drum is thus unobstructed except for the driver rods, these rods are continuously beaten by the grinding balls or the material being ground so that no residue can adhere to the rods in a manner to adversely affect the ground product. The rods are, of course, subject to heavy wear, so that they must be exchanged periodically. Being mounted in bearings in the end walls of the drum as provided in accordance with the invention in a manner that they can be readily replaced through the end walls from the outside, the exchange or repair operation does not involve any considerable plant interruptions.

The increase in production achieved with the subject of the application is surprisingly great. Exhaustive tests have shown that with plant conditions being the same, production increases up to 50% can be attained when driver rods in accordance with the invention are used.

Known ball mills are provided with built-in conformations either on the wall of the drum, on the shaft or the like to obtain satisfactory efficiency, and these are sub ject to heavy wear and it is necessary at corresponding time intervals to exchange the rods which necessitates opening ofthe mill and corresponding interruptions in plant operation. While the rods in accordance with the invention, which are simple driver rods extending through the end walls of the drum, are also subject to heavy wear, it is possible to replace them without difficulty and without any interruption in plant operation of any consequence.

In accordance with the invention the driver rods may be arranged parallel to the axis of the drum and it is desirable 'to place the individual rods at different distances from the axis of the drum. In this manner it is possible by means of the rods to impart increased movement to the charge of the grinding bodies or balls and to the material being ground.

It is particularly advantageous to arrange the driver rods at acute angles with respect to the axis of the drum. For this purpose the driver rods may be arranged in planes extending through the axis of the drum. The position at an acute angle of the rods in a plane extending through the axis of the drum results in that the driver rods when entering the heap of the. grinding bodies and of the material being ground is not heavily and evenly engaged over its entire length, but nevertheless, the desired mixing effect is increased.

If the driver rods are arranged at acute angles with respect to the axis of the drum in such a manner that they are not disposed in planes extending throng-h the axis of the drum, the additional advantages areobtained that the rods do not immediately enter the heap of the grinding bodies and of the material being ground over their entire length, but they enter the heap gradually and progressively. As a result a sudden loading of the driver rods is avoided and the evenness of the rotary movement of the entire drum is improved. Additionally, this manner of arranging the driver rods provides an improvement of the mixing movement of the balls and of the material being ground in a direction axially of the drum. It must be considered that in plants it is customary to install an entire row of such ball mills in axial arrangement at short distances from one another for the purpose of saving space. The arrangement of the driver rods at an acute angle inside of the ball mill permits the exchanging of the driver rods also if the distance between adjacent ball mills is short.

In accordance with the invention, it is recommended in all cases to mount the driver rods in their bearings with tolerance, i.e., to journal the driver rods rotatably in the end walls of the drum. When the driver rods are subjected to loads during grinding operations, the rods are thus caused to rotate about their own axes. This means that equal wear of the driver rods is obtained and their life is correspondingly prolonged. By means of rotating movement of the driver rods, the bearings of these rods in the end walls are also continuously kept clean. Wedging or clogging of the driver rods is thus avoided and the possibility of exchanging each rod is advantageously influenced. 7

Furthermore, it is preferred that the driver rods are disposed in bearing sleeves in the end walls which are closed from the outside by means of plugs. Thus, any fastening means for the driver rods in the interior of the drum are unnecessary, such as built in means which would be readily soiled and would be difiicult to service. As a result, the exchangeability of the rods is provided in a particularly favorable manner because upon removal of the closure plugs from the outside of the end walls, the driver rods can be readily withdrawn from the outside through the bearings.

Further objects and advantages of the invention will become apparent if reference is had to the accompanying drawings which show embodiments of the subject of the invention and in which:

FIG. I is a longitudinal cross-section through a ball mill provided with driver rods arranged at equal distances from the axis of the drum and parallel to the axis of the drum;

FIG. 2 is a cross-section through a ball mill in which the distance of the driver rods from'the drum axis differs;

FIG. 3 again is a cross-section through a ball mill in which the driver rods extend at acute angles with respect to the axis of the drum and in planes which extend through the drum axis;

FIG. 4 is a longitudinal view of a ball mill in which one of several driver rods is illustrated by way of example which extends at an acute angle with respect tothe drum axis but is disposed outside of any plane extending through the drum axis.

The ball mill comprises the two end walls 1 and the drumcasing 2. The end walls 1 are provided with journal shafts 3 which are supported in bearings 4. The driving of the drum is effected by way of the front Wheel 5. The driver rod 6 extends with its ends through corresponding bores in the end walls 1. Both ends of the driver rod 6 in accordance with the upper half of FIG. 1 are provided with threads. This type of rod 6 is tensioned in the interior of the drum by means of nut 7 and bythe cap nut 8 which serves as the closure plug.

A difierent manner of securing the driver rods is illustrated in the lower half of FIG. 1. V is loosely disposed with its ends which are not threaded in thebearing sleeves 10, the outer openings of which are closed by closure plugs 11. The last mentioned type of bearing .for the driver rods also permits of rotary movement of the rods. 7

In the cross-sectional illustration in accordance with FIG. 2 the embodiment of the invention provides for the driver rod 6, 9' being disposed at different distances from the imaginary axis a of the drum.

In the embodiment in accordance with FIG. 3 the driver rods 12 are supported in the bearing sleeves 13 in end Walls 1 while closure plugs 14 are applied to the sleeves 13 in a manner similar to that explained in connection with the driver rods 9 in accordance with FIG. 1. However, the driver rods 12 in accordance with FIG. 3 are disposed at acute angles with respect to the center axis Here the driver rod 9 a of the drum, but in planes which extends through the center axis a.

In the embodiment in accordance wit-h FIG. 4, the driver rod 15 which is indicated in dashes is arranged at an acute angle with the imaginary axis a of the drum but contrary to the embodiment in accordance with FIG. 3 in a manner that the rod 15 is not in a plane which extends through the axis a of the drum.

Having now described my invention with reference to the embodiments illustrated in the drawings, I do not wish to be limited theretoybut what I desire to protect by Letters Patent is set forth in the appended claims.

I claim:

-1. In a ball mill comprising a drum containing a charge of grinding balls and having opposite end walls, a casing extending between said end walls, journal-ling means disposed externally of said end walls, driver rods extending intermediate said end walls through the interior of said drum and movable with said drum and relative to said gn'nding balls to increase the grinding capacity of said mill, and bearing means for individual ones of said rods provided in said opposite end walls, including at least one bearing opening outwardly through one said end wall adapted to receive a rod and permitting removal and replacement of said rod through said end wall.

2. In a ball mill comprising a drum containing a charge of grinding balls and having opposite end walls, a casing extending between said end walls, journalling means disposed externally of said end walls, driver rods extending intermediate said end walls through the interior of said drum and movable with said drum and relative to said grinding balls to increase the grinding capacity of said mill, and bearing means for individual ones of said rods provided in said opposite end walls, including at least one bearing opening outwardly through one said end wall adapted to receive a rod and permitting removal and replacement of said rod through said end wall, said driver rods extending parallel to the axis of said drum and at different distances therefrom.

3. In a ball mill comprising a drum containing a charge of grinding balls and having opposite end walls, a casing extending between said end walls, journalling means disposed externally of said end walls, driver rods extending intermediate said end walls through the interior of said drum and movable with said drum and relative to said grinding balls to increase the grinding capacity of said mill, and bearing means for individual ones of said rods provided in said opposite end walls, including at least one bearing opening outwardly through one said end wall adapted to receive a rod and permitting removal and replacement of said rod through said end wall, said driver rods extending being disposed at different distances from the axis of said drum in planes extending through the axis of said drum and at acute angles relative thereto.

4. In a ball mill comprising a drum containing a charge of grinding balls and having opposite end walls, a casing extending between said end walls, journaliing means disposed externally of said end walls, driver rods extending intermediate said end walls through the interior of said drum and movable with said drum and relative to said grinding balls to increase the grinding capacity of said mill, and'bearing means for individual ones of said rods provided in said opposite end walls, including at least one bearing opening outwardly through one said end wall adapted to receive a rod and permitting removal and replacement of said-rod through said end wall, said driver rods extending being disposed at different distances from the axis of said drum in planes other than planes extending parallel to the axis of the drum and at acute angles relative to said axis.

5. In a ball mill comprising a drumcontaining a charge of grinding 'balls'and having opposite end walls, a casing I ding between said end walls, journalling means disposed externally of said end walls, driver rods extending intermediate said end walls through the interior of said drum and movable with said drum and relative to said balls to increase the grinding capacity of said mill, and bearing means for individual ones of said rods provided in said opposite end walls, including at least one bearing opening outwardly through one said end wall adapted to receive a rod and permitting removal and replacement of said rod through said end Wall, said rods being mounted in said bearing means with tolerance to permit rotation of said rods in said bearing means.

6. In a ball mill comprising a drum containing a charge of grinding balls and having opposite end Walls, a casing extending between said end Walls, journalling means disposed externally of said end Walls, driver rods extending intermediate said end Walls through the interior of said drum and movable with said drum and relative to said grinding balls to increase the grinding capacity of said mills, and bearing means for individual ones of said rods provided in said opposite end Walls, including at least one bearing opening outwardly through one said end Wall adapted to receive a rod and permitting removal and replacement of said rod through said end wall, said rods being mounted in said bearing means with tolerance to permit rotation of said rods in said bearing means, and said bearing means including sleeves defined in said end Walls and closure plugs mounted on said sleeves exteriorly of the end Walls of said drum.

Referenaes Cited in the file of this patent UNITED STATES PATENTS 1,724,441 Weir Aug. 13, 1929 2,041,318 Berger May 19, 1936 2,669,268 Meyer Feb. 16, 1954 2,755,502 Herr July 24, 1956 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No, 3315 451 January 2 1961 Paul August Goeser It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, lines 52 and 67 strike out "extendingfl each occurrence.

Signed and sealed this. 24th day of April 1962.

(SEAL) Attest:

ESTON Go, JOHNSON DAVID L. LADD Attesting Officer Commissioner of Patents 

